The full plastic bottles were thrown from a vehicle into oncoming traffic on Highway 12 and Occidental and Llano roads, the CHP reported.

"All the incidents have taken place in the same general area," said CHP Officer Jon Sloat. "The investigation is unfolding as we speak."

Throwing objects at a moving vehicle is a misdemeanor offense, but if someone is injured, it becomes a felony, he said.

"It is an extremely dangerous thing to do," Sloat said.

The drivers of the damaged vehicles described the suspect as the driver of a mid-2000s white pickup truck with no camper shell.

In the latest incident, a West County Transportation school bus was traveling on Occidental Road at Piezzi Road at 1 p.m. on Thursday when it was struck by a water bottle, sustaining damage to the driver's side mirror.

On Wednesday, officers responded to the first report about 11:25 a.m. from the driver of a bob-tail truck who was traveling west on Highway 12 near Irwin Lane when someone in a passing vehicle threw a full bottle of water through his windshield. It left a softball-sized hole and covered the driver with glass but he was able to pull safely to the side of the road, the CHP reported.

While investigating the first incident, CHP dispatch received two more calls, one from the driver of a Geo Metro who was heading south on Llano Road when his car was struck by a bottle that broke off the driver's side mirror.

A third victim reported having a bottle thrown through his windshield — also leaving a softball-sized hole — while he was driving his Chevrolet mini-van westbound on Highway 12 near Merced Avenue.

The CHP is asking for anyone with information regarding the incidents to call 588-1400.